OAKLAND, Calif. (KGO) -- President Trump signed two actions Tuesday to advance the construction of the Keystone XL and Dakota Access oil pipelines, and East Bay Representative Barbara Lee took to Twitter to voice her opposition.

The signatures could have an immediate impact on the Dakota Access project, which had been halted by the Army Corps of Engineers after the Standing Rock Sioux Tribe demanded that the pipe not go under a dammed section of the Missouri River - a source of drinking water for the tribe.

"They don't create that many jobs. They are disastrous for our air, for our water, for our climate," Sara Shor with 350.org said.

Environmental activists promised to keep fighting the projects. "If the people who put their money into this pipeline don't support it, that's another way that we could stop it regardless of the fact that Trump doesn't care about the planet or the people," Oakland City Councilmember Rebecca Kaplan told ABC7 News. Kaplan spent a week protesting in North Dakota.

Former President Obama had rejected the Keystone XL project after being convinced that the method of turning tar sands into oil contributed to more greenhouse gases.

Mr. Trump said all new projects would have to use American steel.

Glen Stevick with Berkeley Engineering and Research says the materials have improved significantly. "So these advances in the material and material detection or detection of problems has made pipelines much safer than they used to be, and consequently almost certainly safer than putting oil in rolling stock," Stevick said.